Operations on the human or animal eye lens belong to the operations most frequently carried out worldwide. Such operations become necessary as a result of pathological processes which mostly affect the interior of the eye lens, such as clouding of the eye lens (cataract formation) and/or hardening of the lens nucleus in presbyopia or if a change in the refractive power of the lens/eye is to be achieved. With modern surgical methods the interior of the eye lens (nucleus, epithelium) is removed, normally by opening the lens capsule sac only at the anterior face and otherwise leaving it alone. However, in some cases the capsule sac is intentionally opened at both the anterior and posterior faces.
The empty capsule sac remaining after removal of the interior of the natural eye lens is then generally used to accommodate an artificial intraocular lens (IOL) which replaces the removed interior of the eye lens and restores the vision of the patient, taking into account the desired optical correction of the eye. The centered alignment, shape, size and stability/integrity of the anterior opening of the capsule sac (capsulorhexis and/or rhexis) assume particular importance here. The rhexis is one of the factors which is decisive for the result of the entire operation. Its stability/integrity is important for the progress of the operation itself. The aim is to achieved a round rhexis without ridged edges, tears or inhomogeneities, as this will form a stable hole in the capsule sac. As a result, the capsule sack does not tear during the operation despite manipulations inside the lens interior. If this stability/integrity of the rhexis is not ensured, tears can arise in the capsule sac which can result in complications during the operation (e.g. loss of lens material into the vitreous humour space, difficulty to impossibility of implanting an artificial intraocular lens IOL, prolapse of the vitreous humour, etc.). Centered alignment, shape and size of the rhexis are also important for the post-operative result. This is because the capsule sac experiences a postoperative shrinking process, which can vary greatly between individuals. Lens epithelium cells remaining in the capsule sac can migrate, divide and agglomerate. The so-called “secondary cataract” can lead to distortion of the capsule sac and clouding of the remaining parts of the capsule. The posterior lens membrane can become grown over with epithelium cells, become cloudy and severely impair the vision. A central hole must then be cut behind the implanted intraocular lens (IOL) in the posterior capsule membrane, usually with an Nd YaG laser, to clear the optical axis again. The surgeon usually tries to keep the size of the rhexis during lens operations to between 4 and 5.5 mm. Too small a rhexis can lead to subsequent complications (capsular phimosis) in just the same way as too large a rhexis compared to the IOL (OIL lens becoming caught in the rhexis, and off-centerdness of the IOL). A rhexis which is off-center from the IOL, which does not cover the front of the IOL in a circular manner, can lead to pressure by the shrinking rhexis edge on the IOL lens and to the IOL being off-center. The same applies if the shape of the rhexis is not round.
In addition to the rhexis described above, which should usually be as a round a hole as possible centered in the front of the capsule sac (other more oval forms of the rhexis may also be appropriate in certain situations), a posterior rhexis is also created in some cases. This is also a circular hole, in the posterior face of the lens capsule. The same considerations apply in principle for a posterior rhexis as for an anterior rhexis. A posterior rhexis is technically more difficult to accomplish, however, and more risky from a medical aspect. The anterior part of the vitreous body is in direct contact with the posterior capsule and the anterior vitreous membrane should not be injured by a posterior rhexis.
Previous methods of opening the eye lens capsule have been based on mechanical procedures or optical methods, in other words laser surgical methods, particularly involving the use of a femtosecond laser. The simplest mechanical methods are carried out purely mechanically. These entail introducing a needle or forceps into the anterior chamber of the eye. This then perforates the anterior capsule and a more or less round, centered hole of approx. 5 mm diameter is made in the anterior capsule (rhexis or capsulotomy). The centered alignment, shape, size and stability/integrity of the capsular rhexis produced in this manner depend greatly on the skill of the surgeon and the conditions in each individual case. The manual methods can also be assisted by devices such as the Fugo Blade® or Cystotome®. However, these methods still have the disadvantage, among others, that all they can do is produce a point-shaped perforation at a particular place. The surgeon still then has to create the complete, usually circular, cut in the capsule by hand by guiding the device over the capsule in as circular a motion as possible of the required diameter.
Devices are also known that use thermal/electrical effects to cut the capsule open (WO 2010/141181 A1). This has the disadvantage of introducing electric current into the eye and also heating up the ocular tissue.
Optical cutting/perforating of the lens capsule using ultra-short pulse laser systems is already in clinical use. This makes use of the interaction with tissue of ultra-short pulse lasers. The perforation is created by non-linear effects of the ionisation/plasma formation in the ocular tissue at extremely high photon densities. The expansion of the cavitation bubble this causes finally tears the tissue locally. Clinically, postoperative perforation of the anterior capsule as secondary cataract treatment is usually done with Nd YaG lasers, which emit infra-red laser pulses in the nano- or picosecond range with J of energy,
One new development is the use of femtosecond lasers for capsulotomy during the operation. These lasers emit radiation mostly in the near-infra-red or ultraviolet range. Pulses from a few fs to several hundred fs are emitted. This allows successful precise cutting of the ocular tissue with a considerably smaller energy input (individual pulses are in the μJ range). The capsulotomies that can be achieved this way are very stable, centered and circular. However, the patient's eye has to be firmly connected to such a laser device for this. The patient has to be placed under the laser device and the patient's eye held by suction. This prolongs the operation time and procedure. In addition, the devices are very large, demand considerable maintenance, and are expensive. However, clinical trials have confirmed the considerable value of a centered, round and integral rhexis as can be produced with a femtosecond laser.
The capsule exhibits considerable elasticity (E modulus is approx. 1.3 N/mm2). This has to be taken into account during mechanical perforation/cutting of the capsule. Cutting heads, among other things, are therefore described that attach to the capsule by suction during the cutting process (WO 2009/140414 AI). These have a number of disadvantages: Attaching to the lens capsule by suction within the eye is not without risks, since the liquid reservoir in the anterior chamber of the eye is limited and the anterior chamber can therefore collapse, thereby damaging the ocular tissue. This is particularly likely because the suction device in the eye has to operate with the corresponding vacuum, and must therefore be quite large and non-portable.
A medical instrument for use in cataract surgery and a method to be carried out with it are known from US 2004/0092982 A1, in which a cutting element in the form of a cutting ring that can be inserted into the interior of the eye is arranged on a handle that remains outside the eye, the handle being connected to a flexible shaft by means of which a rotary motion from an external motor is introduced into the instrument to drive the cutting ring. The instrument is relatively bulky and not easy for the surgeon to handle.
U.S. Pat. No. 5,269,787 discloses a cutting ring arranged on a shaft to produce an opening in the anterior capsule of the human eye, in which the shaft is connected to an ultrasound source in order to impart vibrations to the cutting ring and thereby perforate the anterior capsule.
Both known instruments share a common feature in that they need to be held and manipulated by the surgeon on the handle or shaft respectively during the cutting process, which means that every incorrect manipulation inevitably affects the cut to be made. With these devices, the kinetic energy to perform the cut is transmitted to the cutting ring by having the said cutting ring mechanically coupled to the drive, which necessitates various components such as couplings, flexible shafts and the like. This has the disadvantage that the drive energy for cutting element has to be transmitted into the eye by means of moving parts, i.e. the drive and cutting element are joined together mechanically. This means that rotating moving parts, which therefore give off heat, must be introduced into the eye through a cut.
All of the patents and patent applications referenced herein (and any English equivalences thereof) are hereby incorporated by reference for showing the same and form part of the specification of this application.